You've already got the DX 7. I'd consider getting another 2.4ghz receiver for your hobbistar. Set up your dx with a model program for each plane. Be sure you've selected the right plane before flying!

Sell the futaba and it's receiver to fund the new 2.4 receiver. All your servos will still work with the new receiver.

The other way would work too, but you end up flying an obselete transmitter (I do fly a 6exa myself) and the DX7 either gets sold or sits on a shelf. Again, it'd just be a receiver purchase, batteries, servos and switch harnesses are interchangable.

J